1. Technical Field
The present disclosure relates to light communication techniques, and, more particularly, to a light communication system, a transmitter and a receiver.
2. Description of Related Art
In optical communication systems and radio frequency (RF) communication systems, the optical characteristics and the RF characteristics are quite different. In the RF communication systems, designs and selections of the “antennas” or precoding techniques can be used to change the equivalent channel in order to enhance the transmission capability of the RF communication system. Such design concepts in the optical communication system have not yet been developed, but the “antennas” in RF communication are analogous to the “lens” of optical communication as optical lens may be used as a transmission medium for the light.
Light-emitting diodes (LEDs) play an important role in the optical communication systems. In recent years, LEDs have achieved significant improvement in terms of performance and brightness, and gradually replace the traditional light sources, such as fluorescent lamps and incandescent lamps. Due to their fast response, LEDs are not only used in lighting systems, but are also used for data transmission.
In terms of data transmission, a transmitter and a receiver in an optical communication system are used for transmission and reception of signals, respectively. Specifically, the transmitter may use the light emitted by an LED to carry signals, and the receiver may use a fixed-focus lens together with a photodiode or a photodetector to receive the light emitted by the LED and decode the signals from the received light.
However, in the above known technique, the receiver (such as a mobile communication apparatus) may move freely in the space, but the fixed focus lens can only provide a fixed focal length and a fixed axial direction. These cannot not be adjusted in accordance with the movement of the receiver, so as a result, the light emitted by the transmitter is scattered or focused with low optical density on the light-emitting diode or the photodetector, resulting in poor quality of the signals received by the receiver and lowering of the transmission capacity of the optical communication system.
Therefore, how to solve the above shortcomings of the prior art has become an important issue for those skilled in the art.